The present invention relates generally to tubular incandescent lamps, and pertains, more particularly, to such lamps as applied in photo-reproduction processes.
A photocopy machine typically employs two different types of lamps, one being referred to as an exposure lamp and the other as a fusing lamp. The exposure lamp is purely for light emitting purposes during the exposure phase of operation. The fusing lamp on the other hand is primarily for heating purposes to xe2x80x9csetxe2x80x9d the toner employed in the photocopy machine. In accordance with the present invention, the principles thereof are applied primarily in connection with a fusing heater lamp, but may also be applied to other general heating purposes.
Fusing heater lamps are typically of single filament construction and have a length corresponding to the maximum size (length) of paper that is to be reproduced. More recently, fusing heater lamps utilize two filaments disposed and electrically connected in parallel within a quartz envelope in order to allow substantially higher operating wattage to be achieved by simultaneously energizing both filaments. The use of parallel filaments provides higher heat density per unit area of envelope wall. However, these types of fuser heater lamps do not provide for selective activation of the filaments to adjust for different voltage output requirements.
Photocopier""s used in both the United States and Europe operate at two different voltage ranges, namely 120 and 240 volts respectively, but each require the same amount of energy in the fuser lamp for fixing the toner (i.e. fusing) onto the copy of the original document. In U.S. Pat. No. 4,710,676 to Morris et al, a dual length filament incandescent lamp is provided that allows for switching between two different levels of total lamp energy at a single voltage to adjust for different incremental wattage output requirements. The specification of Morris et al (U.S. Pat. No. 4,710,676) is hereby incorporated by reference.
What would be desirable is a single tubular incandescent lamp without modification that can run on two different voltage ranges for heating applications for universal that use different voltage standards.
It is, therefore, a primary object of this invention to enhance the tubular incandescent lamp art and particularly that art involving lamps having more than one filament.
It is another object of this invention to provide an improved incandescent lamp wherein the lamp is readily adapted for use in either United States or European markets having different voltage standards.
In accordance with one aspect of this invention, there is provided a fuser lamp comprising first and second filaments having equal resistance and a switching mechanism for connecting a power supply to the fuser lamp. The switching mechanism connects the first and second filaments in a parallel configuration when the voltage is 120 Volts and connects the first and second filaments in series when the voltage is 240 Volts from the power supply.